Spawning behavior of snubnose darters (Percidae) in natural and laboratory environments

Eight species of snubnose darters (genus Etheostoma) were observed and filmed to compare the spawning behavior in the field and in aquaria. These darters exhibited substrate searching, male lateral quivers, and head jabbing behavior in both the field and aquaria. In streams, snubnose darters attached eggs singly to cobble and larger rock substrates, while in aquaria several species were found to attach eggs to fine aquarium gravel as well as cobble and larger rocks. In general, these results support previous aquarium studies of snubnose darters. Information on spawning behavior in snubnose darters as well as darters of the closely related subgenus Etheostoma is synthesized in order to address the phylogenetic affinities of some species in this group of fish.     

Spawning behavior of Arctic charr (Salvelinus alpinus): Spawning synchrony,vibrational communication,and mate guarding

A mismatch in synchrony between male and female gamete release in external fertilizers can result in reduced or failed fertilization, sperm competition, and reduced paternity. In Arctic charr (Salvelinus alpinus), males can adopt either a guard or sneak tactic resulting in both pre‐ and postcopulatory competition between males with alternative reproduction tactics. Here, spawning behavior of free‐living Arctic charr was video‐recorded, and their reproductive behavior was analyzed. From evaluating 157 spawning events, we observed that females mainly spawned with a guarding male and that the female and the guarding male synchronized timing of gamete release under sperm competition. Although sneakers spawned with higher synchrony than the guarding male in single‐male spawning events, the average sneaker released his milt less synchronized with the female than the guarding male under sperm competition. Approximately 50% of the recorded spawning events occurred under sperm competition, where each event included an average of 2.7 males. Additionally, sneakers were more exposed to sperm competition than guarding males. An influx of males, in close proximity to the female, occurred during the behavioral sequences leading up to egg release, but this influx seemed not dependent on egg release, suggesting that something else than gonadal product attracts sneaker males to the spawning female. Just before and during the actual release of gametes, the spawning couple vibrates their bodies in close contact and it seems likely that this vibrational communication between the spawning couple, which results in a larger amplitude sound wave than seen under regular courting, reveals time of gamete release to sneaker males. Thus, vibrational communication may enable synchrony between the guarding male and the female, and this might be traded against the cost of higher detectability from surrounding sneaker males, eavesdropping in close proximity.     

Spawning behavior of the kissing loach (Leptobotia curta) in temporary waters

The natural spawning behavior of the kissing loach, an endangered species of Botiidae, was investigated in the wild in early June for two years in relation to several environmental factors. Kissing loaches spawned in temporary waters after elevation in water level. All spawnings observed (n=163) occurred within 3-5.5 hours from late afternoon to night after formation of the temporary water. These spawnings were performed by one female and one (71%) or two (29%) males in densely vegetated lentic waters. The female and following male(s) swam into dense grasses, where they vibrated to spawn intermittently. After the vibration continuing for 3-20 seconds, they moved to other parts of the dense grassy area and began vibration again. This sequence of spawning behavior was usually repeated several times, and the eggs were thus scattered widely. The spawning behavior and the rapid larval development of this species appear to be adaptations for the use of temporary waters as a spawning ground. The rise in water level and the consequent formation of temporary waters appear to be crucial triggers for reproduction of the kissing loach.     

Spawning behavior of the pygmy leatherjacket Brachaluteres jacksonianus (Monacanthidae) in southeastern Australia

Spawning behavior of the pygmy leatherjacket Brachaluteres jacksonianus was studied in southeastern Australia. Prespawning females thrust the snout repeatedly into spawning substrata, while males exhibited courtship display and nuzzled the female’s face. The females and males touched their abdomens in pairs and released gametes. No parental egg care was observed after spawning. Fertilized eggs measured 0.74 mm in diameter, and each clutch contained 50–191 eggs. The eggs were attached to filamentous red algae, which were found on the surface of the seagrass and other substrata. Reproductive ecology of B. jacksonianus is similar to that of congeneric Brachaluteres ulvarum, although selection of spawning substrata differed in two species.Supplementary material to this paper is available in electronic format at http://dx.doi.org/10.1007/s10228-005-0272-8     

Spawning behavior ofChaetodon multicinctus (Chaetodontidae); pairs and intruders

Synopsis Spawning by the banded butterflyfish,Chaetodon multicinctus (Chaetodontidae) was observed on coral reefs off Kona, Hawaii. These fish occurred in male-female pairs during normal daytime activities, a behavior which is typical for the family. Courtship is also a paired male-female activity. During spawning, however, other individuals (males?) may intrude on the spawning pair. Spawning typically takes place at least a meter or two above the bottom. The spawning position consists of the male below and behind the female with his snout against the female's ventral flank or anal fin area. Intruding individuals may join in when the pair is in position and about to spawn. Intruders line-up against the male in the same position as he is against his female. Underwater photographs are included to illustrate these behaviors.     

Spawning periodicity and annual breeding seasons of Tilapia nilotica (L.) in the White Nile

Two annual breeding seasons are indicated for populations of T. nilotica in the White Nile: a major autumnal season (mid-July–September) coinciding with the annual rainfall and a smaller back-up season in February–March. During these seasons reproducing females constituted 80% and 40% of the total population of mature females compared to 10–12% in the intervening summer period. Enhanced gonadal development, fecundity and GSI values characterized the breeding seasons. Gonadal maturation proceeded uninterruptedly even during the summer and repeated fractional spawning is suggested for this species within and beyond the breeding seasons. Most of the spring breeders were either very young or relatively old fish and most medium-sized females bred in the main autumnal season. Older fish were less fecund (by 70–75%) compared to younger fish. In the latter, fecundity increased progressively with body growth (r² = 0.732; p<0.001); the proportionality was lost in medium-sized fish and in older females (0.9–1.5 kg) fecundity correlated negatively with increased body size.     

Spawning behavior of the collared knifefish, Cymolutes torquatus (Labridae) in Papua New Guinea

A colony of about 10 males and nearly 50 females of Cymolutes torquatus was found living over a sandy substrate on the northwest coast of Normanby Island, Papua New Guinea at depths 14.6 to 18.3 m. Each male appeared to maintain a harem territory, approximately 10 to 14 m², with 4 or 5 females living in sub-units of this territory. Eleven matings of 4 males with 2 to 4 females each were observed on 9 and 10 April 1993. The broadcast spawning of C. torquatus is similar to that of razorfishes in the genus Xyrichtys, but in contrast to most tropical sand-dwelling fishes which mate at dawn or dusk, C. torquatus mated mid-morning between 9:38 to 10:50 h. Sexual dichromatism, color changes during mating, and cleaning of C. torquatus by juvenile Halichoeres zeylonicus are documented with color photographs.     

Same school,different conduct: rates of multiple paternity vary within a mixed‐species breeding school of semi‐pelagic cichlid fish (Cyprichromis spp.)

Mating system variability is known to exist between and within species, often due to environmental influences. An open question is whether, vice versa, similar environmental conditions entail congruent mating behavior, for example in terms of multiple paternity, in species or populations sharing largely comparable breeding modes. This study employed microsatellite markers to investigate the incidence of multiple paternity in Cyprichromis coloratus and Cyprichromis leptosoma, two sympatric, closely related, mouthbrooding Lake Tanganyika cichlids with similar ecological and behavioral characteristics including the formation of open‐water schools. Mouthbrooding females of both species were collected from the same mixed‐species breeding school at the same time, minimizing environmental variation during courtship and mating. In C. coloratus, four of 12 broods had more than one sire, with a mean of 1.33 reconstructed sires per brood. C. leptosoma exhibited multiple paternity in 18 of 22 broods, with a mean of 2.59 or 2.86 reconstructed sires per brood according to the programs gerud and colony , respectively. In addition, two broods were found to contain offspring transplanted from another brood. There was no significant difference in brood size between species, but mean sire number did differ significantly. Hence, substantial similarity in reproductive behavior along with shared environmental conditions during courtship and spawning did not lead to equal rates of polyandry or sneaking in the two species.     

Spawning substrata are important for breeding habitat selection but do not determine premating reproductive isolation in three sympatric Hexagrammos species

Habitat use and spawning substrata were surveyed to characterize the contribution of habitat divergence to reproductive isolation in greenling Hexagrammos species. The spawning substrata and microhabitat in breeding territories differed amongst the three Hexagrammos species studied: H. octogrammus, H. agrammus and H. otakii used small red algae, surfgrass and bryozoans, respectively, as spawning substrata, and breeding territories were established in areas where those substrata were abundant. In contrast, non-territorial individuals were observed in a comparatively wider range of habitats than conspecific territories. Consequently, the distributions of non-territorial individuals of the three species partially overlapped. Since hybrids have been frequently collected, the difference in spawning substrata and the subsequent microhabitat divergence in breeding territories do not prevent females from encountering males of other species. Thus, in addition to habitat divergence, other factors such as behavioural differentiation may be needed to complete premating reproductive isolation amongst these three Hexagrammos species.     

Spawning period and migration of three species of cyprinids in a stream with Mediterranean regimen (SW Spain)

These studies investigated the effects of somatostatin on gastric motility in the rainbow trout. Two experimental models were used, the isolated vascularly-perfused stomach and isolated strips of gastrointestinal smooth muscle. Both models demonstrated that somatostatin can inhibit gastrointestinal motility and may therefore modulate gastric emptying in fish.
In the vascularly-perfused stomach, somatostatin (10–1000 n m ) decreased maximum and baseline intragastric pressure by 10–20% in the presence of stimulatory doses of carbachol or 5-hydroxytryptamine. In addition, somatostatin (1 μ m ) inhibited by 50% the magnitude of spontaneous contractions generated by distension. Somatostatin had little effect on the pressure gradient or contractile frequency. These results suggest that somatostatin may negatively modulate gastric emptying in the rainbow trout.
In isolated gastric smooth muscle strips, somatostatin (100 pmol) inhibited tension stimulated by carbachol (circular orientation of muscle) or 5-hydroxytryptamine (longitudinal orientation). These results correlated with those observed in the vascularly perfused stomach preparation. Somatostatin also decreased tension stimulated by carbachol and 5-hydroxytryptamine in intestinal smooth muscle strips, suggesting that under some conditions somatostatin could increase gastric emptying rate by relaxing intestinal musculature.     

Seasonally of adult male japanese macaques (Macaca fuscata): Androgens and behavior in a confined troop

Seasonal variations in levels of serum testosterone, dihydrotestosterone (DHT), reproductive behavior, and social behavior were investigated in 12 adult males (5 to 20 + years of age) of the Oregon troop of Japanese macaques (Macaca fuscata). Blood samples were collected at 2- to 4-month intervals, and behaviors were monitored twice weekly over a 15-month period. Significant seasonal variations in levels of testosterone and DHT, and in frequencies of mount series, ejaculations, number of female partners, displays, courtship, and aggression were observed. Seasonal variations in reproductive and social behaviors did not correlate with seasonal variations in androgen levels because seasonal increases in these behaviors followed seasonal increases in the androgens with a 1- to 2-month delay. However, significant correlations between increased androgen levels and the onset of mating activity occur when mean monthly frequencies of mount series are shifted 1 to 2 months earlier to coincide with the rise in serum androgen levels. The frequency of adult male play and male-male mounting increased significantly when androgen levels were low. We suggest that photoperiod changes may function as a proximate cue in male Japanese macaques which induces a state of biological readiness for mating, and the behavioral consequences (i.e., mating) are then dependent upon the presence of receptive females.     

Spawning of Basilichthys microlepidotus (Jenyns)

Characteristics of the reproductive cycle of Basilichthys microlepidotus (Jenyns), an atherinid fish living in a South American Mediterranean arid zone, are analysed. Specimens 9-170 mm in total length were captured from August 1982 to April 1984 in the Rio Choapa, in northern Chile (31%%45' S, 71°15' W). Analysis of gonadosomatic index fluctuations, and determination of the proportion of mature males and females captured during the study period, allowed the estimation of the duration of the reproductive cycle.
Females 70–170 mm in total length contained 2000–9000 intraovarian oocytes, of which approximately 80% were vitellogenic (100–1300 μm in diameter) and exhibited a polymodal distribution. A further 4 to 15% of the total oocytes, measured 1700–2000 μm in diameter and appeared ready to be spawned. In 30% of the examined ovaries some of the largest oocytes exhibited signs of degeneration, or atresia. Juveniles approximately 30 mm in total length were captured over most of the study period. Results strongly suggest that B. microlepidotus has multiple spawnings.     

Genetic evidence reveals density-dependent mediated success of alternative mating behaviours in the European bitterling (Rhodeus sericeus)

The reproductive success of alternative mating behaviours may vary within and among populations in relation to environmental factors and demographic parameters. We used behavioural and genetic data to investigate how male density affects reproductive success of territoriality and sneaking in the European bitterling (Rhodeus sericeus, Cyprinidae), a freshwater fish that spawns on the gills of living freshwater mussels. Keeping the number of spawning sites constant, we manipulated male densities in laboratory and mesocosm experiments. We showed that sneaked fertilizations were common in R. sericeus, and that they increased significantly with male density. Territorial mating was almost 17 times more successful than sneaking at the lowest male density treatment, and still 2-3 times more successful at intermediate densities. However, both behaviours conferred the same fitness pay-off at the highest male density. While the success of territorial males declined with male density, the success of individual sneaking males remained constant across densities. Notably, the capacity of territorial males to outcompete sneakers by preoviposition sperm loading was the best predictor of male reproductive success, rather than aggression, body size or postoviposition ejaculation.     

Life cycle and nuclear behavior in three rust fungi (Uredinales)

Kuehneola japonica has a microcyclic life cycle with a regular alternation of generations. Single basidiospore inoculations onto Rosa wichuraiana resulted in teliospore production, indicating its homothallic nature. Dikaryotization in a vegetative mycelium in the host seemed to occur through nuclear division that was not followed by septum formation. Karyogamy and meiosis took place through teliospore and metabasidium development; this fungus was considered to reproduce genetically homogeneous progenies. Puccinia lantanae and P. patriniae were also microcyclic in their life cycle; however, these fungi differed from K. japonica in the mode of nuclear behavior. In the former two fungi, both vegetative and reproductive cells were uninucleate. No karyogamy was observed, and nuclear division in the metabasidium development was thought to be mitotic. In P. lantanae, a basidiospore was formed on a sterigma, whereas a whiplike hypha emerged from each metabasidium cell in P. patriniae. Inoculations of Justicia procumbens with a single basidiospore of P. lantanae resulted in teliospore production. The fungus seemed to remain uninucleate, either haploid or diploid, throughout the life cycle. Thus, reproduction was considered to be apomictic. Received: August 16, 2001 / Accepted: October 1, 2001     

Meiotic behavior in nonaploid accessions of Brachiaria humidicola (Poaceae) and implications for breeding

Brachiaria humidicola is a grass adapted to seasonally swampy grasslands in Africa; two cultivars, 'common' and Llanero, are widely used in Brazilian pastures. New cultivars are in great demand in order to diversify current production systems to achieve improved quality and yield. Cytological analyses of 55 accessions of this species available from the Embrapa Beef Cattle germplasm collection revealed that 27 are apomictic and have 2n = 54 chromosomes. Chromosome pairing as bi- to nonavalent associations at diakinesis indicated a basic chromosome number in this species of x = 6, as found in other closely related Brachiaria species. Thus, these 27 accessions are nonaploid (2n = 9x = 54). Abnormalities were found in the meiosis of these accessions, at variable frequencies. The most common abnormalities were those related to irregular chromosome segregation, which led to unbalanced gamete formation; but chromosome stickiness, cell fusion, and absence of cytokinesis were also recorded. Although some accessions have a low frequency of meiotic abnormalities, ensuring potentially good pollen viability, these cannot be used in hybridization due to a lack of sexual accessions with the same ploidy level.